Percussion implement



Oct. 17, 1939. G, PlNAZZA 2,176,801

PERCUSSION IMPLEMENT FiledfLJune 8, 1937 Patented Oct. 17, 1939 UNITEDSTATES 2,178,801 PERCUSSION IMPLEMENT Giosu Pinazza, Milan, ItalyApplication June 8, 1937, Serial No. 147,115

Germany June 20, 1936 4 Claims.

In the percussion tools which are operated by means of the centrifugalforces of suitably arranged masses which rotate with uniform veloc--ity, the strength of the resultlng'force that acts 5 upon the percussortakes a course equal to a sine curve, so that the percussor with itsforward stroke, i. e., when it effects the shock, acquires the samekinetic energy as with the back stroke. In order to reduce thedestroying influence which, in practice, with the end of the backstrokeis exerted by the shock that the percussor effects against the bottom ofthe casing of the apparatus-an influence which is to be added to therebound that takes place with the efiicient working shock-ashock-absorbing means, in general a spring, is disposed between the saidtwo parts, which shock-absorber is for the purpose of absorbing thekinetic energy and accumulating it in the form of potential or staticcom- 8 pression energy. 7

Although the particular vehemence of the back shock is thus avoided,there still remains, nevertheless, a considerable inconvenience. As thesaid damping means in its turn supports itself against the bottom of thecasing, it exerts upon the bottom a static pressure which has a tendencyto press the casing backwards. As long as the worker who is operatingthe apparatus is in a position to exert an equal or greatercounterforce, the casing does not recede; but when the worker is nolonger able to resist the said force, the casing falls back. As aconsequence, after the first blow the shocks no longer take place at thesame moment at which the speed of the percussor passes through itsmaximum, but with a lag, i. e., when the velocity is alreadydiminishing. As each lag is now added to each preceding lag, the workingpossibility and the efficiency of the apparatus will finally, after acertain relatively limited number of shocks, fall to practicallyunserviceable values. As the lag of the apparatus is in inverseproportion to the mass of the casing, this mass could be enlarged, butthe apparatus would thus become excessively heavy; and besides, alimited lag would still occur. Therefore in order to remove suchinconveniences there would in reality be no other possibility but toreduce the operating force so far that the back shock will becomeinferior to the force which could be brought up as a counter-effect onthe part of the worker, and which amounts to about 50 to 60 kilograms.Taking also into consideration the fact that each spring has adefinitive natural period of vibration, by which fact one is forced tochoose a frequency of stroke which is smaller than the natural vibrationfrequency of the spring, it will easily be evident that movablepercussion implements of this kind in their present state could renderonly very restricted services and would extraordinarily fatigue theworker who operates such apparatus.

The object of the present invention is to provide percussion apparatusin which the abovementioned inconveniences are entirely removed, and inwhich therefore operating forces could be applied which are even higherthan the counterforce which the worker could produce, and this withouttherefore being compelled to increase the weight of the apparatus and,in which, moreover the frequency of stroke could be brought up to a veryhigh value. Furthermore, by the help of the present invention, it ispossible to regenerate a particularly large part of the energy which isaccumulated .in the damping means with the return stroke, and, finally,a long active stroke of the percussor is obtained, that means acorrespending increase of its kinetic energy.

The invention consists essentially in the feature that the casing at itsposterior part, by means of a compressed gas chamber, that is, a chamberinto which a suitably compressed gas is filled, finds itself incommunication with the posterior part of the percussor. Similarly at thefront part, that is, at the percussion end, a. conveniently fixedelastic means is inserted between the casing and the tool, which ismeant for taking up the shock, the said means being designed to returnboth the said elements into one and the same position relative to eachother at the end of each stroke. In this way the desired result, thatis, the fact that the frequency of the stroke could be increased atwill, is obtained, because the cushion of air has no period of naturalvibration, and because the lag will every time be compensated with everystroke before the retrogression which is caused by the next strokeoccurs.

In the accompanying drawing two examples of embodiments of the inventionare shown.

Figure 1 shows diagrammatically the manner of working of the apparatus;

Fig. 2 is a side sectionalview of one embodiment of the inventionshowing the percussor in striking engagement with the tool;

Fig. 3 is a view of the same embodiment of the invention similar to Fig.2, but showing the percussor in the retracted position;

Fig. 4 is a fragmentary sectional view of the same embodiment, taken atright-angles to Fig.

Fig. 5 is a side sectional view of another embodiment of the inventionshowing the percussor in striking engagement with the tool;

Fig. 6 shows a section along line A--A of Fig. 5;

Fig. 7 shows a section along line BB of Fig. 6.

The invention comprises not only the principal inventive idea but alsothe details of the relative conformation.

In the embodiment illustrated in Figures 2 t0 4, two equal masses m arerotating with constant speed and with a movement which is entirelysymmetrical in relation to the percussion axis pp, the symmetricalmovement may be obtained for instance with the help of correspondingtoothed. wheels 2', 7' driven, for example, by a flexible shaft a. Thesaid masses revolve on circumferences of radius 1' around the shafts 0,01, which are carried by a percussor M, that can move freely within acasing N. Should there he .a greater number of gyrating masses, thesecould always be regarded as equivalent to two masses, rotating under thesaid conditions. As is well known, the rotating masses, under thecondition explained above, develop an alternating resultant force, theintensity of which varies according to a sine curve, which isrepresented by the curve in Figure 1. The speed which the percussorobtains is represented by the curve 0. At the moment at which the shocktakes place, and at the moment of the rebound against the bottom of thecasing, this speed suddenly becomes equal to zero. The curve srepresents the path traversed by the percussor, the total path beinggiven by the distance S between the two positions (ax-x in Fig. 2 anda:--:c' in Fig. 3) of axesdrawn across the centres of rotation.

According to the invention, the percussor M is provided at its backwardend with a piston 2, which glides in a fluid-tight manner in a cylinder3. The end of this cylinder, which is disposed at the posterior end ofthe gear casing, is at a distance I (Fig. 2) from the position which thesurface of the piston occupies at the beginning of the stroke. Thisdistance I is longer by the amount 0 than the total piston stroke S. Asthe piston effects its return stroke, the gas or air which isfilled intothe chamber 4 with an initial pressure 170 will be compressed, wherefroma counter-force is produced, the intensity of which may be representedby the curve P1 in Fig. 1. The force that acts upon the percussor willbe the algebraic sum ofthe values ',f and P1, which sum is given by thecurve F1. By this force the movement of the percussor is graduallyretarded so that the speed no longer follows the curve v,

sition a:'--m' as shown in Fig. 3, the percussor has still a certainspeed, which will be braked by the further compression of the gas whichfills the chamber 4 and by the reversal of the resulting centrifugalforces. At the point -z (Fig. 1, beyond the point 1r, a stationary statewill be reached, so that the return stroke will last more than half aperiod, while the duration of the forward stroke will be correspondinglyreduced; The result of this is that the travel is brought to a maximum,and that at the same time the velocity of the subsequent forward strokewill be increased from v to V2.

In the following forward stroke the active force F2 is the algebraic sumof the forces f and P2, where P2 denotes the expansion energy of the gasin the cylinder 3.

The distance covered during the forward stroke and the return stroke isrepresented by the curves S1 and S2.

Obviously the retardation 1-2 is a function of the initial pressure P0of the gas contained in the cylinder 3; hence it is possible to regulateone of these values by conveniently adjusting the other. It is importantto make the retardation as great as possible without varying the totalduration of the cycle.

So far as the resilient cushion between the fore part of the percussorand the posterior part of the tool 5 is concerned, this cushion in thepresent instance is simply formed by two loaded springs land 8, whichbear at one end against the opposite side. of a ring 6, which isprovided at the foot of the tool 5, and at the other end againstshoulders 9 and I0 provided in the prolongation of the casing N, whichcarries the tool. These two springs work against one another andcontinually bring the casing back into the same position relative to thetool, as the tool, when it receives the shock from the percussor M, actsby means of its ring 6 upon the spring, and thus takes the casing alongin the same direction. In this way the casing, at the beginning of thecounter-effect which the gas exerts during the following return stroke,will always find itself in the same initial position. By convenientlychoosing the dimensions and the initial charge of the respective springsin relation to the moving means, the effect of the spring can be madeabsolutely perfect.

In the example of embodiment shown in Figs. 5 to '7, three single masseshave been employed, namely a mass mi in the middle and two masses mrespectively above and below the middle one, whereby all the axes ofrotation are parallel to one another and. at'right angles to thepercussion axis: The masses are connected with one another by means ofthe toothed wheels i1 and :ii, one of which is driven by means of aflexible shaft I4. Here, moreover, means are provided for obtaining aturning motion of the percussor, namely by means of helical grooves II,which act upon a muff I2. This latter, in its turn, acts in a knownmanner only in one direction upon a tool rest I3. In this case the head51 of the tool is not circular but rather of a polygonal form.

The compressed gas is admitted into the chamber 41 through a conduit I5,which opens into the chamber through a duct I6. This latter iscontrolled by a valve IT. The duct I5 has a branch I8, which leads toachamber I9, within which the percussor T runs. The cross-section of thebranch conduit I8 can be regulated by control means, e. g., a screw 20.The degree of compression produced in the chamber 41 depends on thecross-section of the conduit I8. In effect, when this cross-section islarge the gas arriving through conduit I5 can easily escape throughconduit I8 and consequently the pressure of the gas in conduit I5decreases and the gas is admitted under reduced pressure into chamber 4.If on the other hand the cross-section of conduit I8 is small the gasarriving through conduit I5 can hardly escape through conduitI8 andconsequently the pressure in conduit I5 increases and the gas isadmitted under high pressure into chamber 4.

The gas which passes through the duct I8 can be employed for cleaningthe point of the tool. For this purpose holes 2| are provided in thepercussor, through which holes the gas passes from the chamber I9 to theinterior of the percussor, and from there, through a. duct 22 in thehelical grooves ll and the head 51 of the tool, to

the point of the tool.

The chamber 41 in which the piston 21 slides is arranged .as in theprevious case in the rear end 31 of thercasing N1 of the apparatus.

What I claim is:

1. A percussion implement comprising in combination a casing; apercussor slidable axially in ning of every compression stroke, andresilient means connecting said tool to said front part of the casing;whereby the energy of said percussor in its backward stroke ismomentarily stored and then returned to said percussor in the next,forward stroke of the latter to supplement the energy imparted to saidpercussor'by said weights, the total energy is transmitted to said toolby said percussor at the impact and part of. said total energy isexpended by said tool through said resilient means in order to returnsaid casing to I its initial position.

2. A percussion implement comprising in combination a casing; apercussor slidable axially in 7 said casing; eccentric weights rotatablymounted on said percussor and adapted to impart a reciprocatory motionto said percussor by their centrifugal forces; a siidable in the frontpart of said casing and actuated by said percussor; and meanscomprising: a hollow cylinder at the rear part of said casing, a pistonsecured to the rear end of said percussor and adapted to slide in saidcylinder and means for supplying gas to said cylinder so that the gas insaid cylinder always has the same pressure at the beginning of everycompression stroke, and resilient means connecting said tool to saidfront part of the casing and constantly tending to return said tool andsaid front part of the casing to the same relative positions; wherebythe energy of said per'cussor in its backward stroke is momentarilystored and then returned to said percussor in the next, forward strokeof the latter to supplement the energy imparted to said percussor bysaid weights, the total energy is transmitted to said tool by saidpercussor at the impact and part of said total energy is expended bysaid tool through said resilient means in order to return said casing toits initial position.

3. A percussion implement comprising in combination a casing; apercussor slidable axially in said casing; eccentric weights rotatablymounted on said percussor and adapted to impart a reciprocatory motionto said percussor by their centrifugal forces; a tool axially slidablein the front part of said casing and actuated by said percussor; andmeans comprising: a hollow cylinder at the rear part of said casing, apiston secured to the rear. end of said percussor and adapted to slidein said cylinder and means for supplying gas to said cylinder so thatthe gas insaid cylinder always has the same pressure at the beginning ofevery compression stroke, and resilient means connecting said tool tosaid front part of the casing, said resilient means consisting of twoloaded counter-acting springs; whereby the energy of said percussor inits backward stroke is momentarily stored and then returned to saidpercussor' in the next, forward stroke of the latter to supplement theenergy imparted to said percussor by said weights, the total energy istransmitted to said tool by said percussor at the impact and part ofsaid total energy is expended by said tool through said resilient meansin order to return said casing to its initial position.

4. A percussion implement comprising in combination a casing; apercussor slidable axially in said casing; eccentric weights rotatablymounted on said percussor and adapted to impart a reciprocatory motionto said percussor by their centrifugal forces; a tool axially slidablein the front part of said casing and actuated by said percussor;resilient means connecting said tool to said front part of the casing; ahollow cylinder at the rear part of said casing; a piston secured to therear end of said percussor and'workmg in said cylinder; means forsupplying gas under pressure to said cylinder; means for supplying thegas under pressure to said tool for cleaning purposes; and means forregulating the pressure at which gas is admitted in the said cylinderconsisting of means for controlling the cross-section for the passage ofthe compressed gas to the said tool; said resilient means soco-operating with said piston and said cylinder that the energy of saidpercussor in its backward stroke is momentarily stored and then returnedto, said 'percussor in the next, forward stroke of the latter tosupplement the energy imparted to said percussor by said weights, thetotal energy is transmitted to said tool by said percussor at the impactand part of said total energy is expended by said tool through saidresilient means in order to return said casing to its initial position.

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